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RESOURCE LETTER
        Resource Letters are guides for college and university physicists, astronomers, and other scientists to literature, websites, and other teaching aids.
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        introduce nonspecialists to this field. The Resource Letters Editorial Board meets at the AAPT Winter Meeting to choose topics for which Resource
        Letters will be commissioned during the ensuing year. Items in the Resource Letter below are labeled with the letter E to indicate elementary level
        or material of general interest to persons seeking to become informed in the field, the letter I to indicate intermediate level or somewhat specialized
        material, or the letter A to indicate advanced or specialized material. No Resource Letter is meant to be exhaustive and complete; in time there may
        be more than one Resource Letter on a given subject. A complete list by field of all Resource Letters published to date is at the website
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        to Professor Roger H. Stuewer, Editor, AAPT Resource Letters, School of Physics and Astronomy, University of Minnesota, 116 Church Street SE,
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Resource Letter SPh-1: Solar Physics
          Jay M. Pasachoffa!
          Hopkins Observatory, Williams College, Williamstown, Massachusetts 01267
          !Received 2 March 2010; accepted 22 April 2010"
          This Resource Letter provides a guide to printed literature, listing selected books and articles and
          online resources about scientific and cultural references to the Sun and the related topics of solar
          spectroscopy and space weather. Topics include helioseismology, the chromosphere and corona at
          solar eclipses, sunspots and other solar activity, and total solar irradiance, as well as instrumental
          references including spectroheliographs, coelostats, and observatories on the ground and in space.
          References to general works on heliophysics and plasma physics are minimized. © 2010 American
          Association of Physics Teachers.
          #DOI: 10.1119/1.3429977$


I. INTRODUCTION                                                                     Astrophysical Journal
                                                                                    This flagship journal of the American Astronomical Society
   At the turn of the 20th century, much of astronomy was                           was transferred from the University of Chicago Press to the
positional and phenomenological. Studies of the Sun played                          Institute of Physics !England" in 2009. It was founded in
a major role in bringing astronomy to the astrophysical po-                         1895 by solar astronomer George Ellery Hale and a col-
sition that it enjoys today. Twenty-first-century solar physics                     league. A rapid communications section is known as Astro-
is a vibrant science, with solar telescopes on the ground,                          physical Journal Letters, apj.aas.org or www.iop.org/EJ/
including soon the Advanced Technology Solar Telescope                              journal/apj
being erected in Hawaii on Maui, joining dozens of space-                           Monthly Notices of the Royal Astronomical Society
craft studying the Sun. NASA’s Living with a Star program                           www.ras.org.uk or
positions the Sun as a major influence on space weather and                         www.wiley.com/bw/journal.asp?ref"0035-8711&site"1
thus on the Earth. This Resource Letter does not include
solar energy as an energy resource.                                                 Nature
                                                                                    Perhaps the most prestigious journal for important new re-
                                                                                    sults. Founded in the U.K. by a solar physicist, Norman
                                                                                    Lockyer, in the 19th century. Introductory sections include
                                                                                    news, www.nature.org
II. JOURNALS
                                                                                    Science
                                                                                    A competitor of Nature for prestige in publishing important
                                                                                    new results. A journal of the American Association for the
Solar Physics                                                                       Advancement of Science. Introductory sections include
The major journal in the field, http://www.springer.com/                            news, www.sciencemag.org
astronomy/astrophysics!and!astroparticles/journal/11207                             Astronomy and Geophysics (A&G)
Living Reviews in Solar Physics                                                     A popular journal of the Royal Astronomical Society, U.K.,
An online, continuously updatable review journal, http://                           www.ras.org.uk; www.wiley.com/bw/journal.asp?ref"1366-
solarphysics.livingreviews.org/                                                     8781
Astronomy and Astrophysics                                                          Publications of the Astronomical Society of Japan
The principal European astrophysical journal, a successor to                        The Hinode and other Japanese solar spacecraft have led to
many journals of individual European nations,                                       important articles, http://www.asj.or.jp/pasj/en/index-E.html
www.aanda.org/
                                                                                    Journal of Geophysical Research: Space Physics
                                                                                    Articles about coronal mass ejections, space weather, and
 a"
  Electronic mail: jay.m.pasachoff@williams.edu                                     heliosphere, http://www.agu.org/journals/ja/

890        Am. J. Phys. 78 !9", September 2010                http://aapt.org/ajp            © 2010 American Association of Physics Teachers               890
Geophysical Research Letters                                            !Cambridge U. P., Cambridge, 2004". !A"
Articles about coronal mass ejections, space weather, and          (12) Recent Insights into the Physics of the Sun and He-
heliosphere, http://www.agu.org/journals/gl/                            liosphere: Highlights from Soho and Other Space
Physics Today                                                           Missions, edited by P. Brekke, B. Fleck, and J. D. Gur-
A general journal of the American Institute of Physics; http://         man !The Astronomical Society of the Pacific, San
physicstoday.org                                                        Francisco, 2000". !A"
American Scientist                                                 (13) High Resolution Solar Physics: Theory Observa-
A general journal of Sigma Xi, a scientific-research organi-            tions, and Techniques, edited by T. R. Rimmele, K. S.
zation that honors graduating seniors for their research and            Balasubramaniam, and R. R. Radick !Astronomical So-
maintains research support and programs,                                ciety of the Pacific, San Francisco, 1999". !A"
http://www.sigmaxi.org                                             (14) Whole Sun Month at Solar Minimum, edited by J. G.
                                                                        Luhmann !American Geophysical Union, Washington,
                                                                        DC, 1999" #J. Geophys. Res. 104 !A5", 9673–9910
III. CONFERENCE PROCEEDINGS                                             !1999"$. !A"
   There are many conference proceedings relevant to solar         (15) Solar Physics with Radio Observations, edited by T.
physics. Here I present a representative list, starting with a          Bastian, N. Gopalswamy, and K. Shibasaki !Nobeyama
selection in reverse chronological order and continuing with            Radio Observatory, Kiyosato, Japan, 1998". !A"
all the most recent conference proceedings from the Interna-       (16) The SOHO Mission, edited by B. Fleck, V. Domingo,
tional Astronomical Union and the series from the Astro-                and A. I. Poland !Kluwer Academic, Boston, 1995". !A"
nomical Society of the Pacific. The listings from the Euro-        (17) Solar Coronal Structures, edited by V. Rusin, P. Hei-
pean Space Agency and COSPAR !officially, in a never-used               nzel, and J.-C. Vial !VEDA Publishing House of the
name,      Committee     on    Space     Research;      http://         Solvak Academy of Sciences, Bratislave, Slovakia
cosparhq.cnes.fr" are less complete.                                    1994". !A"

                                                                   A. International Astronomical Union solar symposia
(1) Solar Polarization 5: In Honor of Jan Olof Stenfo,
                                                                   (http://www.iau.org/science/publications/iau/symposium/)
    edited by Svetlana V. Berdyugina, K. N. Nagendra, and
    Renzo Ramelli !Astron. Soc. Pacific, San Francisco,            (18) Physics of Sun and Star Spots, IAU Symposium 273,
    2009". !A"                                                          Ventura, Los Angeles, 2010 !Cambridge U. P., Cam-
(2) First Results from Hinode, Sarah A. Matthews, John                  bridge, UK, 2011", %http://www.csun.edu/PhysicsAnd
    M. Davis, Louise K. Harra !Astron. Soc. Pacific, San                Astronomy/IAUS273.htm&. !A"
    Francisco, 2008". !A"                                          (19) Waves & Oscillations in the Solar Atmosphere:
(3) Subsurface and Atmospheric Influences on Solar Ac-                  Heating & Magneto-Seismology, Symposium 247,
    tivity, R. Howe, R. W. Komm, K. S. Balasubramaniam,                 Isla de Margarita, Venezuela, 2007, edited by. R. Erdé-
    and G. J. D. Petrie !Astron. Soc. Pacific, San Francisco,           lyi and C. A. Mendoza-Briceño !Cambridge U. P.,
    2008". !A"                                                          Cambridge, UK, 2008". !A"
(4) Modern Solar Facilities—Advanced Solar Science,                (20) Solar Activity and Its Magnetic Origin, Symposium
    edited by F. Kneer, K. G. Puschmann, and A. D. Witt-                233, Cairo, Egypt, 2006, edited by Volker Bothmer and
    mann !Universitätsverlag Göttingen, Göttingen, Ger-                 Ahmed Abdel Hady !Cambridge U. P., Cambridge, UK,
    many, 2007", %http://webdoc.sub.gwdg.de/univerlag/                  2006". !A"
    2007/solar_science_book.pdf&. !A"                              (21) Coronal and Stellar Mass Ejections, Symposium 226,
(5) Solar and Stellar Physics Through Eclipses, edited by               Beijing, China, 2004, edited by K. Dere, J. Wang, and
    Osman Demircan, Selim O. Selam, and Berahitdin Al-                  Y. Yan !Cambridge U. P., Cambridge, UK, 2005". !A"
    bayrak !Astron. Soc. Pacific, San Francisco, 2007". !A"        (22) Advanced Solar Polarimetry: Theory, Observation,
(6) New Solar Physics with Solar-B Mission, edited by                   and Instrumentation, edited by Michael Sigwarth
    Kazunari Shibata, Shin’ichi Nagata, and Takashi Sakurai             !Astron. Soc. Pacific, San Francisco, CA, 2001". !A"
    !Astron. Soc. Pacific, San Francisco, 2007". !A"               (23) Recent Insights into the Physics of the Sun and He-
(7) The Physics of Chromospheric Plasmas, edited by Petr                liosphere, Symposium 203, Manchester, United King-
    Heinzel, Ivan Dorotovic, and Robert J. Rutten !Astron.              dom, 2000, edited by P. Brekke, B. Fleck, and J. Gur-
    Soc. Pacific, San Francisco, 2007". !A"                             man !Astron. Soc. Pacific, San Francisco, CA, 2001".
(8) Proceedings of the International Symposium on Solar                 !A"
    Physics and Solar Eclipses (SPSE 2006), edited by R.           (24) New Eyes to See Inside the Sun and the Stars: Push-
    Ramelli, O. Shalabiea, I. Saleh, and J. O. Stenflo !Istituto        ing the Limits of Helio and Astero-Seismology, Sym-
    Ricerche Solari Locarno, Switzerland, 2007". !A"                    posium 185, Kyoto, Japan, 1997, edited by D. W.
(9) The Dynamic Sun: Challenges for Theory and Obser-                   Kurtz, J. Christensen-Dalsgaard, and D. Kurtz !Kluwer,
    vations, edited by D. Danesy, S. Poedts, A. de Groof,               Dordrecht, 1998". !A"
    and J. Andries !SP-600, ESA, Leuven, Belgium, 2005".
    !A"
(10) Coronal and Stellar Mass Ejections, edited by K.              IV. TEXTBOOKS AND MONOGRAPHS
      Dere, J. Wang, Y. Yan !Cambridge U. P., Cambridge,           A. Current advanced textbooks
      UK, 2005". !A"
(11) Multi-Wavelength Investigations of Solar Activity,            (25) Physics of the Solar Corona: An Introduction with
     Proceedings of IAU Symposium 233, edited by A. V.                  Problems and Solutions, M. J. Aschwanden !Praxis,
     Stepanov, E. E. Benevolenskaya, and A. G. Kosovichev               Chichester, UK, 2009", 3rd printing. Comprehensive in-

891       Am. J. Phys., Vol. 78, No. 9, September 2010                                                Jay M. Pasachoff      891
troduction, definitions, and examples and an overall     (42) The Sun, S. Hill and M. Carlowicz !Harry N. Abrams,
       theoretical interpretation. !A"                               New York, 2006". !E,I"
(26)   The Solar Corona, 2nd ed., L. Golub and J. M. Pasa-      (43) The Sun, 2nd ed., M. Stix !Springer-Verlag, Berlin,
       choff !Cambridge U. P., Cambridge, UK, 2009". An              2004". !I,A"
       advanced textbook providing a survey of current          (44) Sun Observer’s Guide, Pam Spence !Firefly, Ontario,
       knowledge of the Sun’s outer atmosphere,                      2004". !E,I"
       %http://www.williams.edu/astronomy/corona&. !A"          (45) Nearest Star: The Surprising Science of Our Sun, L.
(27)   Physics of the Sun: A First Course, Dermott J. Mullan         Golub and J. M. Pasachoff !Harvard U. P., Cambridge,
       !Chapman and Hall, London, 2009". !A"                         2001". For general readers. !E,I"
(28)   Fundamentals of Solar Astronomy, A. Bhatnagar and        (46) The Complete Idiot’s Guide to the Sun, J. M. Pasa-
       William C. Livingston !World Scientific, Singapore,           choff !Alpha, New York, 2003". A personal, light-
       2005". Comprehensive and phenomenological but rela-           hearted survey, including anecdotes. The book is avail-
       tively nonmathematical. !I,A"                                 able as a free download, %www.williams.edu/
(29)   Solar Astrophysics, 2nd ed., P. Foukal !Wiley-VCH,            astronomy/sun&. !E,I"
       Weinheim, Germany, 2004". Theoretical in orientation.    (47) The Cambridge Encyclopedia of the Sun, by K. R.
       !A"                                                           Lang. !Cambridge U. P., Cambridge, UK, 2001". Thor-
(30)   The Dynamic Sun, edited by B. N. Dwivedi !Cam-                ough coverage. !I,A"
       bridge U. Press, Cambridge, UK, 2003". An advanced       (48) Storms from the Sun: The Emerging Science of
       text that gives a thorough overview and contains com-         Space Weather, M. J. Carlowicz and R. E. Lopez !Jo-
       prehensive reference lists.!A"                                seph Henry, Washington, DC, 2000". Concentrates on
                                                                     space weather. !E,I"
B. Current general books with solar coverage
                                                                D. Heliophysics
(31) The Cosmos: Astronomy in the New Millennium, 3rd
     ed., J. M. Pasachoff and A. Filippenko !Cengage-           (49) Heliophysics: Plasma Physics of the Local Cosmos,
     Brooks/Cole, Boston, MA, 2007". A current survey                Vol. 1, edited by Carolus J. Schrijver and George L.
     textbook for college and university students. !E,I"             Siscoe !Cambridge U. P., Cambridge, UK, 2009"; He-
(32) A Field Guide to the Stars and Planets, J. M. Pasa-             liophysics: Space Storms and Radiation: Causes and
     choff !Houghton Mifflin Harcourt, Boston, MA, 2006".            Effects, Vol. 2, edited by Carolus J. Schrijver and
     Includes observing lists and observing instructions for         George L. Siscoe !Cambridge U. P., Cambridge, UK,
     eclipses. !E,I"                                                 2010", Heliophysics: Evolving Solar Activity and the
(33) Foundations of Astronomy, 11th ed., M. A. Seeds and             Climates of Space and Earth, Vol. 3, edited by Caro-
     D. E. Backman !Cengage-Brooks/Cole, Boston, MA,                 lus J. Schrijver and George L. Siscoe !Cambridge U. P.,
     2011". A current survey textbook for college and uni-           Cambridge, UK, 2010". !A"
     versity students. !E,I"                                    (50) A Performance Assessment of NASA’s Heliophysics
(34) Discovering the Universe, 8th ed., N. Comins !Free-             Program, National Research Council !National Acada-
     man, New York, 2009". A current survey textbook for             mies Press, Washington, DC, 2009".
     college and university students. !E,I"
(35) The Cosmic Perspective, 5th ed., J. Bennett, M.            E. Book for the visually impaired
     Donahue, N. Schneider, and G. M. Voit !Addison-
     Wesley, San Francisco, 2008". A current survey text-       (51) Touch the Sun, Noreen Grice !Joseph Henry, Washing-
     book for college and university students. !E,I"                 ton, DC, 2005". In Braille with figures embossed so that
(36) Astronomy: From the Earth to the Universe, 6th ed.,             the visually impaired can feel the shapes, %www.you-
     J. M. Pasachoff !Cengage-Brooks/Cole, Boston, MA,               candoastronomy.com&. !E"
     2002". More extensive coverage than The Cosmos. !E,I"
                                                                F. Current monographs
C. Current popular solar books
                                                                (52) Astronomical Spectrographs and their History, J.
(37) The Sun, The Earth, and Near-Earth Space: A                     Hearnshaw !Cambridge U. P., Cambridge, UK, 2009".
     Guide to the Sun-Earth System, John A. Eddy                     Spectrography has often advanced through the need for
     !NASA, Washington, DC, 2009", %bookstore.gpo.gov&.              solar observations. !A"
     A well-illustrated contemporary survey of solar science    (53) Theoretical Investigations of Mechanisms for Solar
     and space weather. !E.I"                                        Eruptions: Applications of the Catastrophe Theory
(38) The Sun from Space, K. R. Lang !Springer, Berlin,               to Solar Eruptions, Jun Lin and Terry G. Forbes
     2009". Includes wide coverage of contemporary satel-            !VDM Verlag, NY, 2008". !A"
     lite results. !E,I"                                        (54) Magnetic Reconnection: MHD Theory and Applica-
(39) The Magnetic Universe: The Elusive Traces of an                 tions, Eric Priest and Terry Forbes !Cambridge U. P.,
     Invisible Force, J. B. Zirker !Johns Hopkins U. P., Bal-        Cambridge, UK, 2007". !A"
     timore, MD, 2009". Treats magnetic fields in astronomy     (55) Particle Acceleration and Kinematics in Solar
     in general, not limited to those from the Sun. !E,I"            Flares: A Synthesis of Recent Observations and The-
(40) The Sun, David Alexander !Greenwood Guides to the               oretical Concepts, M. J. Aschwanden !Kluwer Aca-
     Universe, Santa Barbara, CA, 2009". !I"                         demic, Boston, MA, 2002". !A"
(41) Sun, Earth, and Sky, 2nd ed., K. R. Lang !Springer,        (56) Observational Plasma Astrophysics: Five Years of
     New York, 2006". Wide-ranging survey. !E,I"                     Yohkoh and Beyond, edited by Tetsuya Watanabe,

892        Am. J. Phys., Vol. 78, No. 9, September 2010                                             Jay M. Pasachoff      892
Takeo Kosugi, and Alphonse C. Sterling !Kluwer, Dor-      J. History of solar physics
      drecht, 1998". !A"
                                                                (73) The Sun Recorded Through History: Scientific Data
                                                                     Extracted from Historical Documents, J. M. Vaquero
G. Atlases                                                           !Springer, New York, 2009". Important for assessing the
(57) Solar Filtergrams of the Lockheed Solar Observa-                validity of historical data including those relevant to the
     tory, B. Nolan, S. Smith, and H. Ramsey !Lockheed               solar contribution to climate change. !A"
     Solar Observatory, Burbank, CA, 1970". !A"                 (74) The Sun Kings: The Unexpected Tragedy of Richard
(58) Center and Limb Solar Spectrum in High Spectral                 Carrington and the Tale of How Modern Astronomy
     Resolution 225.2 nm to 319.6 nm, J. L. Kohl, W. H.              Began, S. Clark !Princeton U. P., Princeton, NJ, 2007".
     Parkinson, and R. L Kurucz !Harvard-Smithsonian                 A surprisingly exciting biography of an important fig-
     Center for Astrophysics, Cambridge, UK, 1978". !A"              ure in the history of solar observations. !E,I"
(59) The Structure of the Quiet Photosphere and the             (75) A Concise History of Solar and Stellar Physics, J. L.
     Low Chromosphere, edited by C. de Jager !Springer-              Tassoul and M. Tassoul !Princeton U. P., Princeton, NJ,
     Verlag, New York, 1968". !A"                                    2004". !I,A"
(60) The Radiation of the Solar Photosphere from 2000           (76) Exploring the Sun: Solar Science Since Galileo, K.
     Å to 100 !m, D. Labs and H. Neckel !Springer-                   Hufbauer !Johns Hopkins U. P., Baltimore, MD, 1991".
     Verlag, New York, 1968". !A"                                    Brings solar-physics history to the present era. !I,A"
(61) An Atlas of the Spectrum of the Solar Photosphere          (77) Early Solar Physics, A. J. Meadows !Pergamon, New
     from 13,500 to 28 , 000 cm−1 (3570 to 7405 Å), L.               York, 1970". The standard history of solar physics, in-
     Wallace, K. Hinkle, and W. Livingston !National Solar           cluding reprints of 19th century and other papers !I,A"
     Observatory, Tucson, AZ, 1998". !A"
(62) An Atlas of Sunspot Umbral Spectra in the Visible          K. The sun as a star
     from 15,000 to 25 , 500 cm−1 (3920 to 6664 Å), L.
     Wallace, K. Hinkle, and W. Livingston !National Solar      (78) The Sun as a Star, R. J. Tayler !Cambridge U. P., New
     Observatory, Tucson, AZ, 2000". !A"                             York, 1997". Discusses the Sun as an example of more
(63) An Atlas of the Photospheric Spectrum from 8900 to              distant stars. !E,I"
     13600 cm−1 (7350 to 11230 Å), L. Wallace, K. Hinkle,       (79) The Sun and Cool Stars: Activity, Magnetism, Dy-
     and W. Livingston !National Solar Observatory, Tuc-             namos, edited by I. Tuominen, D. Moss, and G. Rüdi-
     son, AZ, 1993". !A"                                             ger !Springer-Verlag, New York, 1990". The Sun in the
(64) Photographic Atlas of the Solar Chromosphere, A.                context of stars like it. !E,I"
     Ambastha and A. Bhatnagar !Udaipur Solar Observa-
     tory, Udaipur, India, 1985". !I,A"                         L. DVDs
(65) Selected Spectroheliograms, Alan Title !California
     Inst. Technology, Pasadena, CA, 1966". !I,A"               (80) Colors and Motions of the Sun, J. M. Pasachoff !Wil-
                                                                     liams College, Williamstown, MA, 2008", a 14-min
                                                                     film including a variety of solar videos from spacecraft
H. Penultimate generation of advanced books
                                                                     and other sources with narration suitable for university
(66) Astrophysics of the Sun, H. Zirin !Cambridge U. P.,             students, %http://oit.williams.edu/wit/video/solar.cfm&.
     Cambridge, 1988". The insightful originator of the Big          !I"
     Bear Solar Observatory explains solar astrophysics. !A"    (81) The Universe—Secrets of the Sun, Episode 1 of the
(67) The Solar Chromosphere, R. J. Bray and R. E.                    History Channel series !History Channel, NY, 2007",
     Loughhead !Chapman and Hall, London, 1974". A                   http://shop.history.com/?v"history_show_the-universe,
     unique discussion of this solar layer. !A"                      %http://www.imdb.com/title/tt1051155/&. !E"
(68) The Solar Granulation, R. J. Bray and R. E. Lough-         (82) Solarmax !Heliograph, Byron Bay, Australia, 2000",
     head !Chapman and Hall, London, 1967". A unique dis-            DVD version of an IMAX spectacular, %http://
     cussion of this solar phenomenon. !A"                           www.helio.com.au/solarmax/&. !E,I"
(69) The Sun, edited by G. P. Kuiper !University of Chi-        (83) Our Mr. Sun, A Frank Capra movie for young people
     cago Press, Chicago, 1953". The chapters on the solar           from 1956, still a popular introduction; includes Donald
     chromosphere and corona remain standard references.             Menzel;      widely      available     online,    %http://
     !A"                                                             www.imdb.com/title/tt0159620/&. !E"
(70) A Guide to the Solar Corona, by D. E. Billings !Aca-
     demic, New York, 1966". Still a standard reference. !A"    V. HELIOSEISMOLOGY

I. Enduring standard solar books
                                                                (84) Journey from the Center of the Sun, J. B. Zirker
(71) Our Sun, rev. ed., D. H. Menzel, !Harvard U. Press,             !Princeton U. P., Princeton, NJ, 2001", paperback,
     Cambridge, 1959". A delightful survey by the distin-            2004; a nontechnical trade book. !E,I"
     guished eclipse veteran and solar physicist, part of the   (85) Music of the Sun: Story of Helioseismology, W. J.
     original Harvard Series of popular books on astronomy.          Chaplin !Oneworld, Oxford, 2006". A nontechnical
     !E,I"                                                           trade book. !E,I"
(72) The Sun, Our Star, R. W. Noyes !Harvard U. P., Cam-        (86) Sunquakes: Probing the Interior of the Sun, J. B.
     bridge, 1982". A part of the Harvard Series, succeeding         Zirker !Johns Hopkins U. P., Baltimore, MD, 2003". A
     Menzel’s book. !E,I"                                            nontechnical trade book. !E,I"

893       Am. J. Phys., Vol. 78, No. 9, September 2010                                                Jay M. Pasachoff      893
(87) “Helioseismology,” J. Christensen-Dalsgaard, Rev.            C. The scientific value of eclipses
     Mod. Phys. 74, 1073–1129 !2002". !A"
(88) “Helioseismology, Asteroseismology, and MHD con-             (105) “Solar eclipses as an astrophysical laboratory,” J. M.
     nections,” edited by L. Gizon and Paul Cally, Solar                Pasachoff, Nature 459, 789–795 !2009". A review ar-
     Phys. 251 !1–2", 1–500 !2008". !A"                                 ticle describing the important role ground-based
(89) “Lecture notes on stellar oscillations,” J. Christensen-           eclipse observations continue to play in the space age,
     Dalsgaard,      %http://www.phys.au.dk/~jcd/oscilnotes/&.          as part of Nature’s coverage of the International Year
     !A"                                                                of Astronomy. !I,A"
(90) “Local helioseismology,” L. Gizon and A. C. Birch,           (106) “Scientific observations at total solar eclipses,” Jay M.
     %http://solarphysics.livingreviews.org/Articles/lrsp-              Pasachoff, Research in Astronomy and Astrophysics 9,
     2005-6/&. !A"                                                      613–634 !2009". A survey of eclipse science and of
(91) “Local helioseismology: Three-dimensional imaging of               scientists’ plans for observing the 2009 total solar
     the solar interior,” L. Gizon, A. C. Birch, and H. C.              eclipse in China. !I,A"
     Spruit, Annu. Rev. Astron. Astrophys. !2010" !in press".
     !A"                                                          D. Eclipse predictions and atlases
(92) “Solar interior rotation and its variation,” R. Howe,
     %http://www.livingreviews.org/lrsp-2009-1&. !A"              (107) Five Millennium Catalog of Solar Eclipses: "1999
(93) Overview:                                                          to +3000 (2000 BCE to 3000 CE), F. Espenak and J.
     %http://soi.stanford.edu/results/heliowhat.html&.                  Meeus, Technical Publication TP-2006-214170,
(94) Websites          and        educational       resources:          NASA, Washington, DC, 2008. Provides information
     %http://solar-center.stanford.edu/heliopage.html&.                 about eclipses over an extended period of time, giving
                                                                        both historical and predictive information, %http://
                                                                        eclipse.gsfc.nasa.gov/SEcat5/SEcatalog.html&. !I,A"
VI. SOLAR ECLIPSES                                                (108) Five Millennium Canon of Solar Eclipses: "1999
A. Main eclipse websites                                                to +3000 !2000 BCE to 3000 CE", F. Espenak and J.
                                                                        Meeus, Technical Publication TP-2006-214141,
(95) International Astronomical Union Working Group on                  NASA,        Washington,      DC,      2006,     http://
     Eclipses, %www.eclipses.info&.                                     eclipse.gsfc.nasa.gov/SEpubs/5MCSE.html. !I,A"
(96) NASA         Website         from      Fred      Espenak,    (109) Annular and Total Solar Eclipses of 2010, F. Espe-
     %eclipse.gsfc.nasa.gov/solar.html&.                                nak and J. Anderson, TP-2008-214171, NASA, Wash-
(97) Eclipse       Website         from     Xavier      Jubier,         ington, DC, 2008, http://eclipse.gsfc.nasa.gov/SEpubs/
     http://xjubier.free.fr/en/site_pages/Solar_Eclipses.html.          2010/rp.html. !I,A"
                                                                  (110) Fifty Year Canon of Solar Eclipses, F. Espenak,
                                                                        NASA Ref. Pub. 1178, Greenbelt, Maryland, rev.
B. Current eclipse books                                                1987, maps and tables, %http://eclipse.gsfc.nasa.gov/
(98) Totality: Eclipses of the Sun, M. Littmann, F. Espe-               SEpubs/RP1178.html&. !I,A"
     nak, and K. Willcox, 3rd ed. !Oxford U. P., Cambridge,       (111) Total and Annular Solar Eclipse Paths: 2001–2020,
     UK, 2008". A survey for the general reader, including              F. Espenak, 2009, %http://eclipse.gsfc.nasa.gov/
     both cultural and scientific references. !E,I"                     SEatlas/SEatlas3/SEatlas2001.GIF&.
(99) Total Eclipses: Science, Observations, Myths and
     Legends, P. Guillermier and S. Koutchmy !Springer/           E. Extent of total, annular, and partial phases
     Praxis, Chichester, United Kingdom, 1999" #trans. from
     Eclipses Totales: Histoire, Découvertes, Observa-            (112) Individual eclipse maps are available through
     tions !Masson, Paris, 1998"$. Includes both scientific              %xjubier.free.fr/en/site_pages/solar_eclipses/5MCSE/
     cultural references. !E,I"                                          xSE_Five_Millennium_Canon.html&. The graph can
(100) Eclipses: 2005–2017: A Handbook of Solar and Lu-                   display the extent of partial eclipse at each location.
       nar Eclipses and Other Rare Astronomical Events,                  Toggles are the following:
       W. Held !Floris, Edinburgh, United Kingdom, 2005"          • &Lmt= x !x set to 1 or 0" will display or not the penumbral
       #trans. from Astronomische Sternstuden !Verlag               limits, maximum on horizon and rise/set curves
       Freies Geistesleben, Stuttgart, Germany, 2005"$. !E,I"     • &Mag= x !x set to 1 or 0" will display or not the equal
(101) Glorious Eclipses: Their Past, Present and Future,            magnitude curves
       S. Brunier and J.-P. Luminet !Cambridge U. P., Cam-        • &Max= x !x set to 1 or 0" will display or not the maximum
       bridge, 2000" #trans. by S. Dunlop from Eclipses, les        eclipse curves
       Rendez-Vous Célestes !Larousse-Bordas/HER, Paris,
       1999"$. A coffee-table spectacular. !E,I"                  F. Eclipses of the decade
(102) The Sun in Eclipse, by M. Maunder and P. Moore
       !Springer, London, 1998". In a series for amateur as-      (113) Total and Annular Solar Eclipse Paths: 2001–2020,
       tronomers. !E"                                                   %http://eclipse.gsfc.nasa.gov/SEatlas/SEatlas3/SEatlas
(103) Eclipse, by D. Steel !National Academy Press, Wash-               2001.GIF&.
       ington, DC, 2001". A popular survey. !E"
(104) Total Solar Eclipses and How to Observe Them, M.            1. Four partial eclipses of 2011
       Mobberley !Springer, New York, 2007". In an observ-
       ing series for amateurs, including personal profiles.      (114) 4 January 2011 Eastern Europe through India, %http://
       !E"                                                              tinyurl.com/2011Jan04&.

894       Am. J. Phys., Vol. 78, No. 9, September 2010                                                  Jay M. Pasachoff     894
(115) 1 June 2011 Greenland, northern Alaska, %http://                   Solar Eclipses, edited by Z. Mouradian and M.
      tinyurl.com/2011Jun01&.                                            Stavinschi !Kluwer, Dordrecht, 1997". The proceed-
(116) 11 July 2011 ocean off Antarctica, %http://tinyurl.com/            ings of a conference held in Bucharest in 1996, in
      2011Jul01&.                                                        advance of the 1999 eclipse that was visible there. !A"
(117) 25 November 2011 New Zealand, Tasmania,                    (124)   First Results of 1999 Total Eclipse Observations,
      %http://tinyurl.com/2011Nov25&.                                    edited by D. N. Mishev and K. J. Phillips !Professor
                                                                         Marin Drinov Academic, Sofia, Bulgaria, 2000".
2. Next central eclipses                                                 About the 1999 total solar eclipse that crossed Europe.
                                                                         !A"
  a. Total solar eclipses.                                       (125)   Solar and Stellar Physics through Eclipses, Pro-
13–14 November 2012, Northeastern Australia                              ceedings of ASP Conference Series 370, edited by O.
3 November 2013, Gabon, Congo, Kenya                                     Demircan, S. O. Selam, and B. Albayrak !Astronomi-
20 March 2015, Arctic, Svalbard                                          cal Society of the Pacific, San Francisco, CA, 2007".
9 March 2016, Indonesia                                                  Eclipses of the Sun and stars. !A"
21 August 2017, U.S.                                             (126)   The Last Total Solar Eclipse of the Millennium in
2 July 2019, Chile                                                       Turkey, edited by W.C. Livingston and A. Özgüç !As-
14 December 2020, Chile and Argentina                                    tronomical Society of the Pacific, San Francisco, CA,
  b. Annular solar eclipses.                                             2000", conf. series 205. !A"
20 May 2012, Western U.S.                                        (127)   Proceedings of the International Symposium on the
10 May 2013, Northeast and Tennant Creek, Cape York, and                 Total Solar Eclipse of November 3, 1994, edited by
   Australia                                                             M. S. Raljevic, F. Zaratti, and J. M. Pasachoff !The
                                                                         National Academy of the Sciences of Bolivia, La Paz,
29 April 2014, Antarctica
                                                                         Bolivia, 1995". !A"
1 September 2016, Gabon, Congo, and Madagascar
26 February 2017, Chile, Argentina, and Angola
26 December 2019, South India, Sri Lanka, and Indonesia          2. Eclipse history
   !Sumatra and Borneo"
                                                                 (128) Empire and the Sun: Victorian Solar Eclipse Expe-
(118) Next U.S. total eclipse. The total solar eclipse of 21           ditions, A. S.-K. Pang !Stanford U. P., Palo Alto, CA,
      August 2017 will cross the United States from the                2002". !E,I"
      Pacific Northwest through parts of Idaho, Wyoming,         (129) Historical Eclipses and Earth’s Rotation, F. R.
      Nebraska, Kansas, Missouri, Tennessee, Georgia, and              Stephenson !Cambridge U. P., Cambridge, UK, 1997".
      South Carolina. Totality at the centerline will                  Shows the value that eclipses have for assessing
      range from about 2 min through 2 min, 35 s,                      Earth’s rotation over thousands of years. !I,A"
      %http://eclipse.gsfc.nasa.gov/SEgoogle/SEgoogle2001/       (130) UK Solar Eclipses from Year 1 (An Anthology of
      SE2017Aug21Tgoogle.html&.                                        3,000 Years of Solar Eclipses), S. Williams !Clock
                                                                       Tower, Leighton Buzzard, United Kingdom, 1996".
G. Eclipses as a test of relativity                                    !E,I"

(119) Einstein’s Jury: The Race to Test Relativity, J. Cre-      3. Penultimate generation of eclipse books
      linsten !Princeton U. P., Princeton, NJ, 2006". De-
      scribes in detail the most famous eclipse in scientific
      history and its well-known ramifications for testing       (131) The Cambridge Eclipse Photography Guide, J. M.
      Einstein’s general theory of relativity as well as pro-          Pasachoff and M. Covington !Cambridge U. P., Cam-
      viding lessons in the philosophy of science. !E,I,A"             bridge, UK, 1993". Discusses eclipses of the 1990s
(120) Harlan’s Globetrotters: The Story of an Eclipse, D.              and how to observe and photograph them. !E"
      S. Evans and K. I. Winget !Xlibris Corporation, Phila-     (132) Eclipse, B. Brewer !Snohomish, Seattle, 1978". !E"
      delphia, 2005". The story of the 1973 eclipse expedi-      (133) The Hidden Sun: Solar Eclipses and Astrophotog-
      tion to Africa to test the general theory of relativity,         raphy, J. Lowenthal !Avon, New York, 1984". !E"
      named as a pun on the name of Harlan Smith, the            (134) Total Eclipses of the Sun, J. B. Zirker !Princeton U.
      observatory director. !E"                                        P., Princeton, NJ, 1995". !E,I"
(121) “Solar eclipses as an astrophysical laboratory,” J. M.     (135) The Under-Standing of Eclipses, G. Ottewell !Astro-
      Pasachoff, Nature 459, 789–795 !2009". This review               nomical Workshop, Greenville, SC, 1991". !E,I"
      article includes references to the latest observational    (136) Total Solar Eclipse: 2008 and 2009, Sheridan Wil-
      verifications of the general theory of relativity from           liams !Bradt Travel Guides, Buckinghamshire, United
      studies of the Sun and other stars. !I, A"                       Kingdom, 2008". !E"
                                                                 (137) Eclipse! The What, Where, When, Why & How
1. Eclipse conference proceedings                                      Guide to Watching Solar and Lunar Eclipses, P. S.
                                                                       Harrington !Wiley, New York, 1997". !E"

(122) Advances in Solar Research at Eclipses from                H. Websites
      Ground and from Space, edited by J.-P. Zahn and M.
      Stavinschi !Kluwer, Dordrecht, 2000". !A"                  (138) %http://www.eclipses.info&. The Website of the Work-
(123) Theoretical and Observational Problems Related to                ing Group on Solar Eclipses of the International As-

895       Am. J. Phys., Vol. 78, No. 9, September 2010                                                 Jay M. Pasachoff     895
tronomical Union and the IAU Program Group on                     tus of sunspot knowledge and the near-simultaneous
        Public Education at the Times of Eclipses, with links             and independent discovery of sunspots in the early
        to maps and other information about observing                     1610s by Galileo, Harriot, and Scheiner, and the battle
        eclipses; includes many links to other websites.                  for priority. !E,I"
(139)   %http://www.williams.edu/astronomy/eclipse&. Eclipse        (150) Solar Active Region Evolution: Comparing Models
        expeditions from Williams College, with links to other            with Observations, edited by K. S. Balasubramaniam
        sources.                                                          and G. W. Simon !Astron. Soc. Pacific, San Francisco,
(140)   The      Solar   Eclipse    Mailing    List.    %http://          CA, 1994". !A"
        tech.groups.yahoo.com/group/SEML/&. An active user
        group of amateurs and professionals interested in solar
        eclipses, including both science and viewing. Instant       A. Latest solar images
        updates or daily summaries are available, or the mes-          The Sun shines every day even though its light does not
        sages can be read online. Sign up at SEML-                  always come through Earth’s atmosphere. Clouds may pre-
        subscribe@yahoogroups.com.                                  vent us on Earth from seeing the Sun, but a spacecraft orbit-
(141)   TOTALITYNewzine. An online semiannual magazine              ing high above us always has the Sun in view.
        of eclipse expeditions                                         Images are available on the World Wide Web on a daily
        !TOTALITYNewzine@aol.com", %http://xjubier.free.            basis. They come from various ground-based observatories
        fr/en/site_pages/Solar_Eclipses.html& or %http://www.       on Earth and from satellites in space. Since it is always day-
        eclipse-chasers.com/totality.html&.                         light somewhere on Earth, we can almost always get a view
(142)   Interactive Eclipse Paths. %http://xjubier.free.fr/en/      of the Sun from a ground-based observatory. And space im-
        site_pages/SolarEclipsesGoogleMaps.html&.                   ages are quickly made available on the World Wide Web.
(143)   Solar eclipse observers’ records. %http://www.clock-           Many images that you see are made through filters that
        tower.com&.                                                 pass only a very narrow band of the spectrum. Typically, an
(144)   Solar eclipse observers’ statistics.                        H-alpha filter in the visible will pass only 0.5 Å or less out of
        %http://www.eclipse-chasers.com/tsechaserlogsums.           the spectrum that extends from 3900 Å in the ultraviolet to
        php&.                                                       6700 Å in the red.

VII. THE SOLAR SPECTRUM                                             (151) %www.spaceweather.com&. Shows a white-light view
                                                                          of the Sun every day, a forecast of flares, links to
                                                                          images and a photo gallery, and other information
(145) Online laboratories on the solar spectrum and                       about space weather.
      H-alpha imaging. %www.williams.edu/astronomy/jay/             (152) %www.solarmonitor.org&. Posts links to the major
      spectrum&. An interactive solar spectrum; can be                    full-disk solar images from spacecraft, including mag-
      viewed at high-resolution and provides a color orien-               netic field, continuum, H-alpha, two coronal EUV
      tation, http://bass2000.obspm.fr/solar_spect.php. !I,A"             lines, and x-rays. A second page !“more instruments”"
(146) Solar Spectrum Atlases from the National Solar                      elaborates with farside results from GONG, STEREO
      Observatory. Lloyd Wallace and colleagues have pre-                 pairs of images, and other images.
      pared a series of atlases from FTS !Fourier transform         (153) NASA’s Marshall Space Flight Center. The sunspot
      spectrometer at the National Solar Observatory" ar-                 cycle and the butterfly diagram are graphed at http://
      chives. These are available in soft-cover for libraries             solarscience.msfc.nasa.gov/SunspotCycle.shtml and
      and as ftp files as digital data. Solar identifications are         %http://www.sidc.oma.be/sunspot-index-graphics/
      given in the bound atlases. These may be obtained                   sidc_graphics.php&.
      from       wcl@noao.edu,          fhill@noao.edu,        or   (154) The Solar Influences Data Analysis Center of the
      lwallace@noao.edu; general reference: L. Wallace et                 Royal Observatory of Belgium, includes the World
      al., Astrophys. J., Suppl. 106, 165 !1996"; %http://                Data Center for the sunspot index, %http://
      www2.nso.edu/staff/wcl/atlases.html&. !A"                           www.sidc.oma.be&. Graphs of sunspots for the current
(147) Calculating the Spectrum, Lecture Notes: Intro-                     cycle or back to 1750 are available by choosing “Sun-
      duction to Non-LTE Radiative Transfer and Atmo-                     spots” at the left and then choosing “Graphs.” Data are
      spheric Modeling, E. H. Avrett, explaining calcula-                 also available at http://sidc.oma.be/sunspot-index-
      tions for spectral lines in situations out of local                 graphics/sidc_graphics.php.
      thermodynamic equilibrium;                                    (155) Sunspot drawings since 1947 and daily high-
      %http://www.cfa.harvard.edu/~avrett&. !A"                           resolution images, Kandilli Observatory, Turkey
(148) Student spectroscopes, distributed by %http://solar-                !click on the symbol for the English translation",
      center.stanford.edu/activities/cots.html&. !I"                      %http://www.koeri.boun.edu.tr/astronomy/&.
                                                                    (156) AAVSO Solar Observing Program. The Solar Com-
                                                                          mittee of the American Association of Variable Star
VIII. SUNSPOTS AND OTHER SOLAR ACTIVITY
                                                                          Observers keeps an AAVSO American Relative Sun-
  Many of the books listed in Secs. III and IV discuss sun-               spot      Index,       %http://www.aavso.org/observing/
spots and solar activity                                                  programs/solar/bulletin.shtml&,                 %http://
                                                                          www.sidc.oma.be/sunspot-index-graphics/
                                                                          sidc_graphics.php&.
(149) The Enigma of Sunspots: A Story of Discovery and              (157) Solar Stormwatch. At solarstormwatch.com, indi-
      Scientific Revolution, J. Brody !Floris, Edinburgh,                 viduals can examine solar images and pick out storms
      Scotland, 2000". Discusses the history and current sta-             as well as help track them. Volunteers look at images

896        Am. J. Phys., Vol. 78, No. 9, September 2010                                                   Jay M. Pasachoff       896
from NASA’s STEREO spacecraft as part of the Citi-               only 62 solar radii of the solar surface. Its images
      zen Science movement, earlier used in Zooniverse                 would include the entire Sun, including the far side
      !www.zooniverse.org", which started with the Galaxy              and the poles: %http://sci.esa.int/science-e/www/area/
      Zoo identification program.                                      index.cfm?fareaid"45&.
                                                                 (179) Synoptic Optical Long-term Investigations of the Sun
IX. SOLAR SPACECRAFT                                                   !SOLIS", a program of the National Solar Observa-
                                                                       tory; %http://solis.nso.edu&.
A. Space satellites
(158) Solar Dynamics Observatory,                                C. Past spacecraft
      %http://sdo.gsfc.nasa.gov&.
(159) Solar and Heliospheric Observatory,                        (180) Yohkoh Public Outreach Project,
      %http://sohowww.nascom.nasa.gov/&.                               %http://www.lmsal.com/YPOP/&.
(160) SOHO gallery, %http://sohowww.nascom.nasa.gov/             (181) Solar Maximum Mission,
      gallery&.                                                        %http://solarscience.msfc.nasa.gov/SMM.shtml&.
(161) TRACE !Transition Region and Coronal Explorer",            (182) Solar Physics at Marshall Space Flight Center !with
      %trace.lmsal.com&.                                               links", %http://solarscience.msfc.nasa.gov/&.
(162) Hinode at NASA’s Marshall Space Flight Center,
      %http://solarb.msfc.nasa.gov&.                             D. Individual current spacecraft instruments
(163) STEREO !at JHU/APL", %http://stereo.jhuapl.edu&.           1. SOHO
(164) STEREO !at NASA headquarters",
      %http://stp.gsfc.nasa.gov/missions/stereo/stereo.htm&.        The Solar and Heliospheric Observatory !http://
(165) Ulysses Probe Homepage                                     sohowww.nascom.nasa.gov/", launched by the European
      %http://ulysses.jpl.nasa.gov/&.                            Space Agency with major participation by NASA, has been
(166) Ramati High Energy Solar Spectroscopic Imager              aloft since 1995. It is located beyond the Moon in the direc-
      !NASA’s Goddard", Education and outreach. %http://         tion of the Sun, where it orbits in a slight halo around the
      hesperia.gsfc.nasa.gov/hessi/outreach.htm&.                Sun-Earth line so that its radio signals are not overwhelmed
(167) Ramati High Energy Solar Spectroscopic Imager              by the solar radio radiation. It contains a dozen instruments,
      !NASA’s Goddard", Homepage.                                including three that often send back hourly images. !1" The
      %http://hesperia.gsfc.nasa.gov/hessi/index.html&.          Extreme-Ultraviolet Imaging Spectrograph (EIT), from
(168) Ramati High Energy Solar Spectroscopic Imager !Ber-        NASA’s Goddard Space Flight Center, sends back four types
      keley", %http://hessi.ssl.berkeley.edu&.                   of image to study the chromosphere and corona.
(169) Ramati High Energy Solar Spectroscopic Imager data         !a" Helium II !that is, ionized helium, given that He I is
      center,                                                          neutral helium" at 304 Å. It shows gas at temperatures
      %http://hesperia.gsfc.nasa.gov/rhessidatacenter/&.               of about 60,000 K.
(170) Imager for Magnetopause-to-Aurora Global Explora-          !b" Iron IX !that is, iron that has lost eight of its electrons"
      tion !IMAGE", %http://image.gsfc.nasa.gov&.                      at 171 Å. It is at a temperature of about 1,000,000 K.
(171) Thermosphere-Ionosphere-Mesosphere-Energetics              !c" Iron XII !that is, iron that has lost eleven of its elec-
      and Dynamics !TIMED",                                            trons" at 195 Å. It is at a temperature of about
      %http://www.timed.jhuapl.edu&.                                   1,500,000 K.
(172) GOES Solar X-Ray Imager,                                   !d" Iron XV !that is, iron that has lost fourteen of its elec-
      %http://www.ngdc.noaa.gov/stp/stp.html& and                      trons" at 284 Å. It is at a temperature of about
      %http://www.sec.noaa.gov/sxi&.                                   2,000,000–3,000,000 K.
(173) NASA Missions, with links %nasascience.nasa.gov/
      heliophysics&.                                             !2" The Large Angle and Spectrographic Coronagraph
(174) NASA’s Living with a Star Program, %http://                (LASCO) from the Naval Research Laboratory sends back
      lws.gsfc.nasa.gov&.                                        images using a “coronagraph,” a device that blocks out the
(175) PROBA2 !Project for Onboard Autonomy-2", an ESA            solar photosphere !the everyday solar surface" to make it
      technology-test microsatellite launched in 2009, car-      possible to see the surrounding corona. Unfortunately, for
      ries two instruments operated by the Royal Observa-        optical reasons it is not possible for the coronagraph’s block-
      tory of Belgium, SWAP !Sun Watcher using APS De-           ing !“occulting”" disk to block out only the photosphere; it
      tectors" and LYRA !Large Yield RAdiometer" for             has to block out a considerable region surrounding the photo-
      x-ray and extreme-ultraviolet solar irradiance; %http://   sphere as well. The photosphere is drawn in for scale and
      proba2.sidc.be/index.html/about/& and the instruments.     orientation in the images displayed. The C1 coronagraph is
(176) PROBA2’s observations of the 15 January 2010 annu-         defunct. The C2 coronagraph blocks the innermost half solar
      lar eclipse: %http://proba2.sidc.be/index.html/outreach/   radius above the solar disk; its field of view extends from 1.5
      documentation/article/proba2-witnesses-an-annular&.        solar radii to about 7 solar radii. The C3 coronagraph blocks
                                                                 the innermost 2.5 solar radii above the solar disk; its field of
B. Future solar satellites and programs                          view extends from 3.5 solar radii out to about 33 solar radii.
                                                                 !The Sun’s radius is about 700, 000 km= 440, 000 miles at
(177) Solar Probe: %http://solarprobe.gsfc.nasa.gov&.            the Sun’s distance of 1 , 500, 000 km= 93, 000, 000 miles."
(178) Solar Orbiter: Solar Orbiter was chosen in 2010 by the     !3" The Michelson Doppler Imager (MDI) and Solar Oscil-
      European Space Agency as one of three missions en-         lations Investigation (SOI) from Stanford University sends
      tering the “definition” phase, the final step before a     back images of the Sun that match ordinary white light,
      mission is chosen. The spacecraft would come within        though they are in a narrow visible-light filter band. The

897       Am. J. Phys., Vol. 78, No. 9, September 2010                                                 Jay M. Pasachoff      897
images can be used to make images that show motions of the       acronym from Solar Terrestrial Relations Observatories.
Sun to use in helioseismology; they also show the sunspots
as they would appear in white light.
                                                                 (189) See:      %http://www.nasa.gov/mission_pages/stereo/
                                                                       main/index.html&.
(183) SOHO’s Website at %http://sohowww.nascom.nasa.             (190) See: %http://stereo.jhuapl.edu/&, STEREO 3-D solar
      gov/& includes links to descriptions of the instruments,         images.
      to educational matters, and to a gallery of past and       (191) http://www.rainbowsymphony.com/sun-3d-anaglyph.
      present images.                                                  html
(184) Up-to-date set of eight images from SOHO:
      %http://sohowww.nascom.nasa.gov/data/realtime/&.           5. Solar Dynamics Observatory


2. TRACE                                                         (192) See: %http://sdo.gsfc.nasa.gov&. SDO was launched on
                                                                       11 February 2010. It carries the following three instru-
                                                                       ments.
(185) NASA’s Transition Region and Coronal Explorer              (193) HMI (Helioseismic and Magnetic Imager), extending
      !TRACE" has been aloft since 1998 to make high-                  the Michelson Doppler Imager on SOHO with full-
      resolution observations of the solar corona as well as           disk coverage at higher spatial resolution, %http://
      of the region of transition between the chromosphere             hmi.stanford.edu/&.
      and corona. Its field of view covers only part of the      (194) AIA (Atmospheric Imaging Assembly), with full-disk
      Sun at one time, but it shows magnetically controlled            imaging at 8 wavelengths every 10 s, extending the
      loops of gas in the corona at exceedingly high detail.           Extreme-ultraviolet Imaging Telescope on SOHO,
      It is a project of the Lockheed Martin Solar and As-             %http://aia.lmsal.com/&.
      trophysics Laboratory, with a telescope built by the       (195) EVE (Extreme Ultraviolet Variability Experiment), to
      Smithsonian Astrophysical Observatory. Its site at               measure the solar extreme-ultraviolet !EUT" irradi-
      http://trace.lmsal.com/POD/NAS2002v2.html shows a                ance, which varies abruptly and which influences
      wide variety of solar images. The TRACE homepage                 Earth’s climate, %http://lasp.colorado.edu/eve/&.
      at %http://trace.lmsal.com/& shows a Picture of the Day
      as well as providing links to other TRACE imagery.         6. Solar X-ray Imager


                                                                 (196) GOES !Geostationary Operational Environmental Sat-
3. Hinode                                                              ellite" Solar X-ray Imager, a solar x-ray imager is on a
   A successor to TRACE and to a defunct Japanese x-ray                NASA weather satellite; devices to monitor the total
solar satellite known as Yohkoh was launched in 2006.                  amount of solar energy reaching Earth are on at least
Called Hinode, the Japanese word for “sunrise,” after its              three satellites, and other spacecraft also play roles in
launch !it had been Solar-B", it carries telescopes built by           studying the Sun. After all, the solar panels on earth-
Lockheed Martin Solar and Astrophysics Laboratory and the              resources spacecraft face the Sun all the time, so the
Smithsonian Astrophysical Observatory and a spectrographic             add-on cost was relatively small. GOES-13 has sent
instrument built at the Mullard Space Science Laboratory in            images since 2006; GOES-14 has sent images since
England and at the U.S. Naval Research Laboratory; it is               2009. See: %http://www.swpc.noaa.gov/sxi/&.
operated in collaboration with the National Astronomy Ob-
servatory of Japan and has European Space Agency and Nor-        7. PROBA2
wegian involvement. The x-ray telescope can image the
whole Sun at a time while maintaining the high-resolution of
TRACE.                                                           (197) SWAP (Sun Watcher using APS Detectors):
                                                                       %http://proba2.sidc.be/index.html/swap/&.
                                                                 (198) LYRA (Large Yield RAdiometer":
(186) The American Hinode site is %http://solarb.                      %http://proba2.sidc.be/index.html/lyra/&.
      msfc.nasa.gov/&.
(187) The Japanese Hinode site is %http://solar-b.nao.ac.jp/     X. GROUND-BASED OBSERVATORIES
      index_e.shtml&.
(188) The link for daily and archival Hinode XRT !x-ray
      telescope" images;                                         (199) National Solar Observatory. It provides live images
      %http://xrt.cfa.harvard.edu/data/latestimg.php&.                 of solar activity through its digital library and hosts an
                                                                       ftp library of past solar activity. It operates the largest
                                                                       U.S. solar telescope !the McMath-Pierce" on Kitt
4. STEREO                                                              Peak, Arizona, and the world’s best instrumented tele-
                                                                       scope !the Dunn Solar Telescope" on Sacramento
   A pair of spacecraft was sent into solar orbit in 2006 to           Peak, New Mexico. See: %http://www.nso.edu/&.
image the Sun simultaneously from two different angles as        (200) Sacramento Peak Observatory/National Solar Ob-
the spacecraft drift apart. Since it gives a stereoscopic or           servatory: H-alpha, continuum, helium; %http://
three-dimensional view, the project is called STEREO, an               nsosp.nso.edu/data/latest_solar_images.html&.

898         Am. J. Phys., Vol. 78, No. 9, September 2010                                               Jay M. Pasachoff       898
(201) ISOON !Improved Solar Observing Optical Network"           B. Mt. Wilson Observatory
      H-alpha, continuum, helium; %http://nsosp.nso.edu/
      VIDEOIMG/isoon/latest_h.jpg&.                                The 150 ft solar tower at the Mt. Wilson Observatory has
(202) NOAO Image Gallery, %www.noao.edu/image_                   been observing the Sun on every clear day since 1912. It is
      gallery/&.                                                 now run by the Mt. Wilson Institute.
(203) Global Oscillation Network Group (GONG),                   (221) Magnetogram/continuum,
      %http://gong.nso.edu&. The U.S. National Solar Obser-            %http://www.astro.ucla.edu/~obs/intro.html&.
      vatory’s project called Global Oscillation Network
      Group adopted the name and the acronym GONG be-
      cause it is used for helioseismology: To detect how the    C. Observatoire de Paris
      solar surface is ringing like a bell. Its network of six
      telescopes around the world has at least one imaging       1. BAse de données Solaire Sol
      the Sun almost always for years at a time.                    H-alpha prominences, K-line on/off center, radio observa-
(204) The latest images showing sunspots and the magnetic        tions, limb prominences !K3 is the center of the K-line of
      field    are    available     at   %http://gong.nso.edu/   ionized calcium; K1v !K1-violet" is about 1 Å blueward of
      Daily_Images/&.                                            K3".
(205) Big Bear Solar Observatory: Global H-alpha net-
      work, %http://www.bbso.njit.edu/Research/Halpha/&.
      The site provides links to the Global H-alpha Net-         (222) See: %http://bass2000.obspm.fr/home.php?lang"en&.
      work, with images from ground-based observatories          (223) SOLIS (Synoptic Optical Long-term Investigations
      around the world.                                                of the Sun), %http://solis.nso.edu/&. Synoptic Optical
(206) Swedish Solar Observatory, La Palma. It arguably                 Long-term Investigations of the Sun at the National
      provides the highest-resolution solar photospheric im-           Solar Observatory": Photospheric magnetic field; he-
      ages, from the Swedish 1-m Solar Telescope. See:                 lium !10,830 Å chromosphere"; calcium !8542 Å in-
      %http://www.solarphysics.kva.se/&.                               frared line".
(207) Ramati High Energy Solar Spectroscopic Imager              (224) NASA’s Goddard Space Flight Center. Includes cal-
      Data Center. See especially its Public Outreach pages            cium, coronagraph, and helium, as well as SOHO, and
      by clicking on the left and see the latest solar images          links;
      at %http://www.solarmonitor.org/rhessidatacenter/&.              %http://umbra.nascom.nasa.gov/images/latest.html&.
(208) Solar science described at NASA’s Marshall Space
      Flight Center, %http://solarscience.msfc.nasa.gov/&.
(209) The sunspot cycle is graphed at                            D. Advanced Technology Solar Telescope
      %http://solarscience.msfc.nasa.gov/SunspotCycle.shtml&.       The Advanced Technology Solar Telescope is being built
                                                                 on Haleakala, Maui, at an altitude of 3050 m !10,000 ft". The
                                                                 decision was made on the basis of the least atmospheric blur-
A. High-quality amateur solar observations                       ring, the most annual hours of low sky brightness, the lowest
(210) %www.meade4m.com& from the Meade Instruments               dust levels, and the smallest temperature extremes of the 72
      Corp.                                                      sites considered.
(211) %www.solarminimum.com&, H-alpha movies from                (225) See: %atst.nso.edu/& Clicking on “Science” will give a
      Gary Palmer.                                                      brochure.
(212) Astronomy        Picture     of    the   Day,    http://      The announcement of the approval of the project by the
      antwrp.gsfc.nasa.gov/apod/. You can search for sun,        National Science Foundation says that “understanding the
      corona, eclipse, or other topics.                          role of magnetic fields in the outer regions of the Sun is
(213) High Altitude Observatory, H-alpha, K-line, helium,        crucial to understanding the solar dynamo, solar variability,
      Mauna       Loa      coronagraph      images,   %http://   and solar activity, including flares and mass ejections, which
      www.hao.ucar.edu/&. It has, at least, daily white light    can significantly affect life on Earth. ATST research will in-
      and K-line images.                                         vestigate solar variability and its impact on terrestrial cli-
(214) Mauna        Loa      Solar     Observatory,    %http://   mate; and the conditions responsible for solar flares, coronal
      mlso.hao.ucar.edu/cgi-bin/mlso_homepage.cgi&.              mass ejections, and other activities that can impact terrestrial
(215) San Fernando Observatory, %www.csun.edu/sfo/&. It          communications and power systems, disrupt satellite com-
      has, at least, daily white light and K-line images.        munications, and endanger astronauts and air travelers.”
(216) Rome Observatory, Solar-Physics Section, %http://
      www.mporzio.astro.it/solare/Lastimages.html&.                   “ATST’s 4-meter !13-foot" primary mirror will
(217) The archive of images obtained since 1996                       feed an advanced array of instruments designed to
      is available at %http://www.mporzio.astro.it/solare/            study the Sun in light ranging from near ultraviolet
      calendarioPSPTa.htm&.
                                                                      !350 nm" into the far infrared !28,000 nm, or 28
(218) Culgoora Solar Observatory (Australia), H-alpha
      low-resolution; %http://www.ips.gov.au/Solar/2/4&.              microns". High-order adaptive optics, pioneered by
(219) Kanzelhoehe Solar Observatory (Austria), %http://               the NSO and its partners at NSO’s Dunn Solar
      www.solobskh.ac.at/&.                                           Telescope at Sunspot, NM, will correct blurring of
(220) Radioheliograph daily images of the Sun; %http://               solar images caused by Earth’s atmosphere and
      solar.nro.nao.ac.jp/&, Nobeyama Radio Observatory,              thus allow ATST to observe features in the solar
      Japan.                                                          atmosphere with unprecedented sharpness, down

899       Am. J. Phys., Vol. 78, No. 9, September 2010                                                 Jay M. Pasachoff      899
to structures only a few tens of kilometers in size.”            !1985",          http://articles.adsabs.harvard.edu/full/
                                                                       1985JBAA…95..270D. !E"
                                                                 (231) J. M. Pasachoff and W. C. Livingston, “Coelostat and
(226) Assorted fact sheets at %ftp://ftp.nso.edu/outgoing/             heliostat: Alignment and use for eclipse and other field
      users/dooling/fact_sheets/&.                                     purposes,” Appl. Opt. 23, 2803–2808 !1984". !I,A"
(227) Executive Briefing package on ATST at ftp://               (232) M. Demianski and J. M. Pasachoff, “Coelostat and
      ftp.nso.edu/outgoing/users/dooling/Brfg/. A DVD on               heliostat: Theory of alignment,” Sol. Phys. 93, 211–
      ATST is available on line as a smaller streaming                 217 !1984". !A"
      video; %http://atst.nso.edu/node/692&.
                                                                 XII. TOTAL SOLAR IRRADIANCE (FORMERLY
XI. SPECTROHELIOGRAPHS AND COELOSTATS/                           SOLAR CONSTANT)
HELIOSTATS
   An older technique can provide very narrow bands of           (233) World Radiation Center/Physical Meteorological Ob-
spectrum, which allows purer isolation of different levels of          servatory     Davos,     under     Projects   %http://
the Sun’s atmosphere, thus allowing more accurate study of             www.pmodwrc.ch/pmod.php?topic"tsi/composite/
motions on the Sun. This technique uses a device called a              SolarConstant&.
spectroheliograph. It was used by the great solar scientist      (234) From ACRIMsat, which carries the ACRIM-3 Active
George Ellery Hale at the turn of the 20th century; Hale went          Cavity Radiometer Irradiance Monitor !ACRIM",
on to build the two largest telescopes in the world in succes-         %http://www.acrim.com&.
sion: first the 100 in. telescope on Mt. Wilson and then the     (235) From SORCE/TIM !SOlar Radiation & Climate
200 in. telescope on Palomar Mountain. !The 200 in. was the            Experiment/Total Irradiance Monitor", %http://
largest in the world through about 1995 when the Keck 400              lasp.colorado.edu/sorce/instruments/tim.htm&.
in.—10 m—telescopes went into use."                              (236) From VIRGO !Variability of Solar Radiation
   In a spectroheliograph, sunlight passes through a narrow            and Gravity Oscillations" on SoHO, %http://
slit and makes a spectrum. A second slit then isolates some            www.pmodwrc.ch/pmod.php?topic"tsi/virgo/proj_
particular wavelength of the spectrum. Next, the two slits             space_virgo&.
scan together from side to side, meaning that the film or,
now, electronic detector behind the second slit builds up an
image of the Sun at the precise wavelength that passes           XIII. SPACE WEATHER
through that slit. An advantage of a spectroheliograph is that
                                                                   Several of the books listed in Parts II and III cover space-
the wavelength passed can be very narrow and pure, and any
                                                                 weather topics.
wavelength at all can be selected. A disadvantage is that the
mechanical scanning is imprecise and takes time, allowing
the Sun to change during a scan.                                 (237) Space Weather Quarterly: The International Jour-
                                                                       nal of Research and Applications !International
  A description of a spectroheliograph, by Raymond N.                  Geopphysical        Union":      %www.agu.org/journals/
Smartt, formerly of the National Solar Observatory, is avail-          spaceweather&.
able online through the McGraw-Hill Encyclopedia of Sci-         (238) Space Weather. www.spaceweather.com. A daily post-
ence and Technology through their website.                             ing that describes the current space weather, including
(228) See: %http://www.accessscience.com&. !Note that a trial          a photograph of the Sun with sunspots, an image of
      subscription or a full subscription may be necessary."           the back side of the Sun, a flare likelihood prediction,
                                                                       and other information and images relevant to space
                                                                       weather. Postings for back days are archived.
1. Coelostats and heliostats                                     (239) Solar Monitor, %www.solarmonitor.org&. A composite
   Coelostats and heliostats are tracking mirrors that enable          set of ground-based and space full-disk solar images,
the telescope and any associated instrumentation !spec-                the most recent from six views on the top-level page,
trograph etc." to remain fixed. They are used in both major            with additional spacecraft images available by click-
solar observatories and on eclipse expeditions. Heliostats             ing.
send the solar image down the polar axis and use a motor         (240) NOAA Space Weather Prediction Center, %http://
that rotates once in 24 h. Coelostats reflect the solar image          www.swpc.noaa.gov/&.
into a secondary mirror that adjusts for the changing solar      (241) Lockheed Martin Master List of Solar Web Sites:
declination !except for days of eclipses, when they can be set         Space        Weather,       %http://www.swpc.noaa.gov/
to match that day’s declination" and because of the reflection         Education/index.html&.
rotate once in 48 h.                                             (242) Magnetosphere,         %http://www-spof.gsfc.nasa.gov/
                                                                       Education/Intro.html&, an educational website by
                                                                       David P. Stern and Mauricio Peredo.
(229) L. M. Dougherty, “A note on the principle and nomen-       (243) Auroras, http://www.gi.alaska.edu, from the Geophys-
      clature of heliostats, coelostats and siderostats,” J.           ical Institute of the University of Alaska, Fairbanks.
      British Astron. Assoc. 92 !4", 182–187 !1982", %http://          %http://www.geo.mtu.edu/weather/aurora& from Michi-
      adsabs.harvard.edu/abs/1982JBAA…92..182D&. !E"                   gan Tech.
(230) L. M. Dougherty, “Heliostats, siderostats and co-          (244) University Corporation for Atmospheric Research,
      elostats,” J. British Astron. Assoc. 95 !6", 270–271             %http://www.windows.ucar.edu/spaceweather&.

900        Am. J. Phys., Vol. 78, No. 9, September 2010                                               Jay M. Pasachoff      900
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